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There are two opposing conventions for the representations of data.
The first of these was first published by G. E. Thomas in 1949 and is followed by numerous authors (e.g., [[Andrew S. Tanenbaum|Andy Tanenbaum]]).<ref name="tanenbaum">{{cite book |author-last=Tanenbaum |author-first=Andrew S. |author-link=Andrew S. Tanenbaum |title=Computer Networks |edition=4th |publisher=[[Prentice Hall]] |date=2002 |pages=274–275 |isbn=0-13-066102-3 |url=https://archive.org/details/computernetworks00tane_2 }}</ref> It specifies that for a 0 bit the signal levels will be low-high (assuming an amplitude physical encoding of the data) - with a low level in the first half of the bit period, and a high level in the second half. For a 1 bit the signal levels will be high-low.
The second convention is also followed by numerous authors (e.g., [[William Stallings]])<ref name="stallings">{{cite book |author-last=Stallings |author-first=William |author-link=William Stallings |title=Data and Computer Communications |edition=7th |publisher=[[Prentice Hall]] |date=2004 |pages=137–138 |isbn=0-13-100681-9 |url=https://archive.org/details/datacomputercomm00stal_1 }}</ref> as well as by [[IEEE 802.4]] (token bus) and lower speed versions of [[IEEE 802.3]] (Ethernet) standards. It states that a logic 0 is represented by a high-low signal sequence and a logic 1 is represented by a low-high signal sequence.
If a Manchester encoded signal is inverted in communication, it is transformed from one convention to the other. This ambiguity can be overcome by using [[differential Manchester encoding]].
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